The invention relates to backplanes used in the electronic and telecommunications industry, and in particular, to a stacked backplane assembly combining two or more backplanes so as to form an integral unit.
In the modern electronic industry, backplanes are commonly used when there is a requirement to interconnect several electronic or optical cards according to a required connection scheme. A backplane is an electronic, optical or opto-electronic circuit board into which other circuit boards (cards) can be plugged in.
The requirements for electronic and optical backplanes in high tech industries have become increasingly complex, resulting in a need to combine different functionality on the same backplane or midplane. For example, modern data communications systems operate at high speed on a backplane, at the same time requiring high current levels to supply power to the system. Unfortunately, combining different functionalities on a single backplane, e.g. both high current layout tracks with high-speed tracks, results in difficult and costly manufacturing implications. While the high-speed signals require fine and precise track widths imprinted with thin copper layers to provide the required controlled impedance characteristics of the backplane, the high current tracks are thick and bulky, and require thick copper layers to control heat build-up in the backplane. As a result, such a complicated backplane that provides multiple types of functionality can be manufactured by a limited number of highly specialized suppliers, and typically has a low yield, and hence high cost.
There have been numerous attempts to solve the above-mentioned problem. In one approach, it has been suggested to separate the power function from the signal function on the backplane and run it on a separate buss bar. A buss bar comprises strips of copper, typically laminated together, and connected to the rear side of a backplane. This approach has its drawbacks, as buss bars are expensive and require extra interconnects to route power from the power source to the electronic cards.
In another approach, it has been suggested to route the power on a secondary backplane, which is mounted behind the signal backplane and attached to the signal backplane with mezzanine connectors. The drawback of this approach is that it requires additional space for the whole system, adds the cost of the mezzanine connectors, and makes the whole system bulky and complex.
Accordingly, there is a need in the industry for the development of an alternative structure for multi-functional backplanes used in electronic, telecommunications and other high technology industries, which would avoid the above-mentioned problems.
It is therefore an object of the invention to provide an improved solution for a multi-functional backplane, which would be simple, cost effective, and easy to manufacture.
According to one aspect of the invention there is provided a stacked backplane assembly, comprising:
at least two backplanes, each backplane having a prime manufacturing reference mark;
the backplanes being assembled so as to form an integral unit in such a manner that the prime manufacturing reference marks of at least two of the backplanes coincide; and
at least a portion of each backplane forming the stacked backplane assembly being accessible to an external device.
Preferably, the backplanes comprising the assembly further comprise secondary manufacturing reference marks, and comprise further tertiary manufacturing reference marks, depending on system requirements, the backplanes being assembled such that at least two of the above-mentioned reference marks coincide.
Beneficially, at least one of the prime, secondary and tertiary reference marks is a manufacturing reference hole or a manufacturing reference point, depending on the backplane requirements and system configuration.
Advantageously, one or more of the backplanes comprising the stacked backplane assembly is a midplane, allowing cards to be plugged into the front and rear side of the midplane and into other backplanes comprising the assembly.
Conveniently, each of the backplanes or midplanes comprising the stacked backplane assembly is an electrical, optical or opto-electronic backplane, according to the requirements of the cards to be interconnected.
Conveniently, the stacked backplane assembly comprises two or three backplanes, depending on the system configuration.
Advantageously, not all the backplanes or midplanes comprising the stacked backplane assembly have the same type of functionality, allowing cards to be plugged in to the assembly so that one card is plugged into one or more backplanes simultaneously.
Conveniently, the backplanes comprising the stacked backplane assembly are selected from power backplane, high-speed electrical signal backplane and high-speed optical backplane functionality type.
Advantageously, the backplanes comprising the stacked backplane assembly are assembled so that the rear side of each backplane or midplane faces the front side of the adjacent backplane or midplane, thus forming a backplane sandwich or stacked backplane assembly.
The backplanes or midplanes comprising the stacked backplane assembly may be manufactured so that not all of them have the same size and shape. This allows a stacked backplane assembly to be constructed according to the geometric requirements of specific cards.
Beneficially, backplanes or midplanes comprising the stacked backplane assembly, are manufactured so that the assembly has a uniform thickness, permitting the use of standard cards manufactured in industry. Alternatively, only the portions of the backplanes that are accessible to an external device may conveniently have a uniform thickness.
Advantageously, the stacked backplane assembly comprises two backplanes, where the rear of the first backplane is adjacent to the front of the second backplane, and where the first backplane is a power backplane, and power is supplied to the power backplane from a power cable attached to a terminal block on the rear side of the power backplane, and the power is distributed to the front sides of the first and second backplanes forming the assembly.
The stacked backplane assembly described above has the following advantages. It is much easier and cheaper to manufacture relatively simple individual backplanes and assemble them together into an integral unit than to manufacture a complicated and labour intensive multi-functional backplane. As a result, the stacked backplane assembly forms a compact and reliable unit, which is inexpensive to produce. Conveniently, the backplane assembly as described above permits one or more circuit boards to be plugged into two or more backplanes or midplanes simultaneously, providing a low-cost solution to the problem of routing both power and data communication or telecommunication signals to an electronic or optical card.